Centrifugal gas compressor



Jan. 9, 1968 J. w. ENDRESS 3,362,624 I CENTRIFUGAL GAS COMPRESSOR FiledSept. 6, 1966 INVENTOR JAMES W. ENDRESS.

F" W-W ATTORNEY.

United States Patent Office 3,352,624 Patented Jan. 9, 1968 3,362,624CENTRIFUGAL GAS COMPRESSOR James W. Endress, Syracuse, N.Y., assignor toCarrier Corporation, Syracuse, N.Y., a corporation of Delaware FiledSept. 6, 1966, Ser. No. 577,215 4 Claims. (Cl. 230-114) ABSTRACT OF THEDISCLOSURE A centrifugal compressor for operation over an extended rangehaving interrelated inlet guide vanes and a diffuser blocking ringmechanism to vary compressor capacity without inducing compressor surge.A valve, operably connected to the guide vanes is arranged to subjectthe opposite sides of the diffuser blocking ring mechanism to compressorsuction and discharge pressure to vary the position of the blocking ringmechanism in the diffuser passage.

This invention relates to gas compression equipment. More particularly,this invention relates to centrifugal gas compressors. Still moreparticularly, this invention relates to centrifugal gas compressorssubjected to large load variations.

One of the major problems arising in the use of centrifugal gascompressors for applications where the compression load varies over awide range is flow stabilization through the compressor. The compressorinlet, impeller and diffuser passage must be sized to provide for themaximum volumetric flow rate desired. When there is a low volumetricflow rate through such a compressor, the flow becomes unstable. As thevolumetric flow rate is decreased from a stable range, a range ofslightly unstable flow is entered. In this range there appears to b apartial reversal of flow in the diffuser passage, creating noises andlowering the compressor efficiency. Below this range, the compressorenters what is known as surge, wherein there are periodic complete flowreversals in the diffuser passage, destroying the efficiency of themachine and endangering the integrity of the machine elements. Since aWide range of volumetric flow rates is desirable in many compressorapplications, numerous modifications have been suggested to improve flowstability at low volumetric flow rates. One of the most accepted andsuccessful modifications has been the addition of guide vanes in theinlet of the compressor to vary the flow direction and quantity ofentering gas. However, since the instability at low flow rates is alsorelated to the diffuser configuration, it would appear desirable to varydiffuser configuration in response to the load on the machine to providea more flexible compressor.

It is therefore the chief object of this invention to provide a methodof varying the capacity of a centrifugal compressor to provide a largerange of stable flow rates.

It is another object of this invention to provide a centrifugal gascompressor having means therein to stabilize the gas flow therethroughat extremely low flow rates.

It is a further object of this invention to provide means forautomatically interrelating inlet guide vane movement with movement ofdiffuser flow restriction means to optimize compressor efficiency over awide range of flow rates.

The objects of this invention are attained by providing a centrifugalgas compressor with inlet guide vanes and diffuser restriction means.

Valve means operable in response to guide vane rotation provide diffusergas pressure on one side of the diffuser restriction means and inlet gaspressure on the other side of the diffuser restriction means to positionthe diffuser restriction means in relation to guide vane position toprovide peak efficiency at any flow rate.

Other objects and features of my invention will be apparent upon aconsideration of the ensuing specification and drawing in which thefigure is an elevational view partly in section of a portion of thecentrifugal compressor including the impeller, inlet guide vanes anddiffuser passage, the compressor incorporating my invention.

Referring more particularly to the drawing, there is shown a gascompressor 1 of the well-known centrifugal type wherein gas to becompressed is induced to flow in an axial direction into a vanedimpeller connected to a suitable driver for imparting rotary motionthereto. As the gas is compressed during its travel through thecompressor, it is directed radially from the impeller to a diffuserpassage communicating with the tip of the impeller. The compressorincludes a housing 2 with inlet passage 3 and diffuser passage 5 formedtherein. Only a portion of the housing is shown, it being understoodthat such a construction is conventional in equipment of the kind underconsideration. An impeller 7 affixed to shaft 9 by nut 11 is provided inhousing 2 between the inlet passage 3 and diffuser passage 5. Inletguide vanes 13 journalled for rotation in housing 2 are positioned aboutthe inlet passage to control the direction and quantity of gas flowtherethrough. Diffuser restriction means comprised of annular ring 15having extension ring 17 bolted thereto by bolts 19 is mounted inhousing 2 for axial movement therein. Sealing members 21 and 23 alongwith O-rings 25 are provided to create pressure tight chambers 27 and29. A cylindrical cavity 31 is formed in annular ring 15 having threeradial cavities 33, 35, and 37 formed in the side wall thereof. Apassageway 39 in annular ring 15 communicates between radial cavity 33and chamber 29. A passageway 41 in annular ring 15 communicates betweenradial cavity 37 and chamber 27. A passageway 43 in annular ring 15communicates between radial chamber 35 and clearance space 45. Acylindrical valve guide 47 having openings 49, 51 and 53 therein alignedwith radial cavities 33, 35 and 37 respectively is securely disposed inchamber 31 preferably by an interference fit.

In order to effect movement of the diffuser ring 15, there is providedactuator means including valve stem 55, mounted for sliding movementwithin valve guide 47. A cylindrical cavity 57 and radial passages 59 invalve stem 55 provide communication between the end of chamber 31nearest the diffuser and housing cavity 61. A plurality of radialpassages 63 in the portion of the housing forming inlet 3 communicatehousing cavity 61 with inlet passage 3. A link 65, mounted on post 66 bypivot pin 67, is operably connected to a valve stem 55 by pivot pin 69.Guide vane arm 71 attached to one of the guide vanes 13 by bolt 73, isoperably connected to link 65 as by ball joints 75 and 77. A control rod79 is mounted for rotation about its longitudinal axis to rotate one ofthe guide vanes 13. Cable 81, interlaced around guide vanes 13 providesan interconnection therebetween to provide simultaneous rotation of allthe guide vanes in response to rotation of rod 79. The control rod 79can be rotated by any well known means (not shown) such as electric,pneumatic or hydraulic positioners responsive to an operating conditionof the compressor, or its associated equipment which is indicative ofthe load on the compressor. Thus if the compressor Were to be used in arefrigeration machine, the positioning means could be responsive to thetemperature of the chilled water leaving the machine, this temperaturebeing related to the quantity of refrigerant being lifted from the lowside to the high side of the machine by the compressor. If thecompressor were being used to compress air, the positioning means couldbe responsive to ambient temperature since this is an indication of theair density and therefore the quantity of air being compressed.

The compressor, with the control arrangement described, functions asfollows. Extension ring 17, attached to annular ring 15, is capable ofaxial movement within diffuser passage 5 to close or partially close thepassage, note the position indicated in dotted lines. Annular ring 15 isbasically pressure balanced due to its configuration. When pressure issupplied to chamber 27, annular ring 15 will move to close the diffuser.When the pressures in chambers 27 and 29 are balanced, the piston willbe stationary. When pressure is supplied to chamber 29, annular ring 15will move to open the diffuser passage. Extension ring 17 along withannular ring 15 are automatically positioned as follows: Movement ofguide vanes 13 by actuator rod 79 will move stem 55 by means of thelinkages heretofore described. If the valve stem is moved to the rightof the location shown in the figure, chamber 27 will be in communicationwith chamber 45 which is at diffuser pressure because of the passagewaybetween the impeller tip and ring 17. The open passage between the twoaforementioned chambers, would consist of passageway 43, radial cavity35, radial cavity 37 and passageway 41. At the same time, chamber 29will be in communication with housing cavity 61 which is at inletpressure due to passages 63. The open passage between cavity 61 andchamber 29 would consist of passageway 39, radial cavity 33 and the leftend of valve guide 47 which is open to cavity 61. The pressure imbalancebetween chambers 27 and 29 would thus move annular ring 15 to the rightuntil the open passageways heretofore described are closed by therelative movement of the valve guide with respect to the valve stem.Movement of the valve stem to the left will result in re versing themovement of annular ring 15. As can be seen from the foregoingdescription, movement of the guide vanes will effect movement of thediffuser restriction means which will result in increasing the liftcapability of the compressor over the complete range of flow ratesattainable.

While I have described a preferred embodiment of my invention, it is tobe understood that my invention is not limited thereto but may beotherwise embodied within the scope of the following claims.

I claim:

1. A centrifugal gas compressor comprising a housing having an inletpassage and a diffuser passage formed therein, an impeller mounted insaid housing between the inlet and diffuser thereof, a plurality ofguide vanes rotatably mounted in the housing to vary the quantity of gasflowing through the inlet passage, diffuser restriction means, mountedfor movement within the diffuser passage to restrict flow of gastherethrough, actuator means for moving said diffuser restriction means,said actuator means including valve means, operable in response to guidevan rotation to provide diffuser gas pressure on one side of saiddiffuser restriction means and inlet gas pressure on the other side ofsaid diffuser restriction means to cause movement thereof.

2. A centrifugal gas compressor according to claim 1 wherein said valvemeans includes a first valve member, a second valve member adapted formovement relative to said first valve member, said first valve memberbeing operably connected to said guide vanes for movement therewith,said second valve member being operably connected to said diffuserrestriction means, movement of said first valve member from anequilibrium position relative to said second valve member causingmoveent of said diffuser restriction means and said second valve memberback into equilibrium position relative to said first valve member.

3. A centrifugal gas compressor according to claim 1 wherein said valvemeans includes a valve body, formed in said diffuser restriction means,a valve stem, adapted for movement relative to said valve body, saidvalve stem being operably connected to said guide vales for movementtherewith, movement of said valve stem from an equilibrium positionrelative to said valve body causing movement of said diffuserrestriction means to move said valve body back into equilibrium positionrelative to said first valve member.

4. A method of increasing the lift capability of a centrifugal gascompressor having an inlet and a diffuser comprising the steps ofproviding a variable restricted inlet:

restricting the flow of gas through the compressor inlet in response tothe load imposed on the compressor,

supplying gas at inlet pressure and diffuser pressure to a control whichis responsive to the inlet gas flow restriction, and

restricting flow of gas through the diffuser in response to apredetermined relation between the inlet and diffuser pressure from thecontrol.

References Cited UNITED STATES PATENTS 1,322,810 11/1919 Moody 103-973,251,539 5/1966 Wolfe et al. 230-414 3,289,919 12/1966 Wood 230-114HENRY F. RADUAZO, Primary Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,362,624 January 9, 1968 James W. Endress It is hereby certified thaterror appears in the above numbered patent requiring correction and thatthe said Letters Patent should read as corrected below.

Column 4, line 6, for "van" read vane line 26, for "vales" read H vanesSigned and sealed this 18th day of March 1969.

(SEAL) Attest:

Edward M. Fletcher, Jr. EDWARD J. BRENNER Attesting Officer Commissionerof Patents

